D. Kray

• Prof. Dr.
• University of Applied Sciences, Offenburg

Mechanized biochar field application remains challenging due to biochar’s poor flowability and bulk density. Granulation of biochar with fertilizer provides a product ready for application with well-established machinery. However, it’s unknown whether granulated biochar-based fertilizers (gBBF) are as effective as co-application of non-granulated b...

Im Zuge des Projektes wurde die Herstellung von Pflanzenkohle und die Schaffung von C-Senken in landwirtschaftlich genutzten Böden als eine von drei Möglichkeiten thematisiert, um die Treibhausgasemissionen zu reduzieren oder zu kompensieren. Aufgrund der vielfältigen Anwendungsmöglichkeiten in verschiedenen Bereichen landwirtschaftlicher Betriebe...

Significant improvements in module performance are possible via implementation of multi-wire electrodes [1]. This is economically sound as long as the mechanical yield of the production is maintained. While flat ribbons have a relatively large contact area to exert forces onto the solar cell, wires with round cross section reduce this contact area...

The use of biochar is an important tool to improve soil fertility, reduce the negative environmental impacts of agriculture, and build up terrestrial carbon sinks. However, crop yield increases by biochar amendment were not shown consistently for fertile soils under temperate climate. Recent studies show that biochar is more likely to increase crop...

As PV enters the terawatt era, reliability, sustainability and low carbon footprint of solar modules are key requirements. The N.I.C.E. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sup> technology from Apollon Solar is a good candidate for significant improvements in these areas. As the second-g...

Whitepaper on biochar and its C sink capabilities. German version.

One promising PV module technology in terms of reducing expensive consumables while keeping the performance on a high level is the N.I.C.E.™ (New Industrial Solar Cell Encapsulation) module technology from Apollon Solar that is based on mechanical pressing contacts. In this paper, we investigate the question if the N.I.C.E.™ module technology is we...

DE 102008051037 A1 UPAB: 20100428 NOVELTY - The method involves producing reference bodies using fracturable material, where the material selected from a group consisting of semiconductor wafer i.e. silicon wafer, solar cell and ceramic material, is used as the fracturable material. Structural damages targeted into a part of the reference bodies ar...

A liquid agent for the surface treatment of monocrystalline wafers, which contains an alkaline etching agent and also at least one low-volatile organic compound. Systems of this type can be used both for the cleaning, damage etch and texturing of wafer surfaces in a single etching step and exclusively for the texturing of silicon wafers with differ...

The invention relates to a method for the precision processing of substrates, in particular for the microstructuring of thin layers, local dopant introduction and also local application of a metal nucleation layer in which a liquid-assisted laser, i.e. laser irradiation of a substrate which is covered in the regions to be processed by a suitable re...

In this paper, we present results of the development of a selective emitter structure for crystalline silicon solar cells suitable for industrial mass production. The process sequence follows the approach first introduced by Volk et al [1]. Laser doping is performed directly after emitter diffusion. In a second step, the emitter is etched back homo...

A method of forming a multi-doped j unction is disclosed. The method includes providing a first substrate and a second substrate. The method also includes depositing a first ink on a first surface of each of the first substrate and the second substrate, the first ink containing a first set of nanoparticles and a first set of solvents, the first set...

In this paper, we present results of the development of a selective emitter structure for crystalline silicon solar cells suitable for industrial mass production. The process sequence follows the approach first introduced by Volk et al [1]. Laser doping is performed directly after emitter diffusion. In a second step, the emitter is etched back homo...

For the fabrication of high efficiency solar cells a full electroplated metallization process is beneficial. In this paper light induced plating (LIP) of thin Nickel seed layers and subsequent Silver metallization has been processed. The antireflective coating is opened by laser chemical doping (LCP). The subsequent front contact was formed by a Ni...

Selective emitters will soon become a standard feature of industrial silicon solar cells. RENA offers a laser chemical process (LCP) to locally ablate the antireflection coating and form a highly doped emitter at the opened area. The front side metallization is then applied by light induced plating (LIP) of nickel and silver. However, it is still a...

The implementation of the selective emitter technology is one of the most attractive changes for industrial solar cell manufacturing. In this paper the pretreatment prior to light induced plating of thin electrodeposited Nickel seed layers and subsequent electrodeposited Silver has been studied. The cell results have been analyzed in terms of ghost...

The investigation of different selective emitter (SE) approaches is a current trend in solar cell manufacturing. The incorporation of a local high phosphorous doping underneath the front contact grid allows for the use of high-sheet resistance illuminated emitters that combine low recombination and improved blue response. Further efficiency increas...

Commercial front-contact solar cells can often be represented as an equivalent circuit with two diodes. A first diode models low-level injection Shockley-Read-Hall recombination in the bulk of the solar cell and associated with an ideality factor of one, while the second diode models several loss mechanisms as depletion region recombination or edge...

In this paper Laser Chemical Processing (LCP) is used for high local doping of selective emitters. In order to find influencing laser parameters on LCP selective emitters, high-efficiency Si solar cells with size of 2x2 cm 2 cells were processed. The highly doped emitters were processed with different laser powers to see the influence on grooving f...

This paper focuses on the analysis of local phosphorous laser doping in high-efficiency solar cells. Those so-called selective emitters are intended to reduce the contact recombination and resistance in order to increase the solar conversion efficiency. Sample solar cells are prepared using laser chemical processing as the laser doping technique an...

In this paper we present experimental data on ultrathin silicon wafer solar cells as well as the analytical description of their open-circuit voltage and fill factor. For this we use the analytical model of Fischer and Plagwitz to describe the rear surface recombination that we extend for very low wafer thicknesses. We observe an unexpected drop of...

This paper deals with the development of a new cutting method for thin silicon solar wafers with liquid-jet-guided lasers (LaserMicroJet®, LMJ, and Laser Chemical Processing, LCP). Several laser systems with different wavelengths were tested to find the optimum laser system and processing parameters in terms of efficient material removal and deep l...

We present investigations on a new technology with which to cut wafers from a silicon ingot, i.e., the laser chemical processing (LCP), formerly known as laser chemical etching. A coupled laser-liquid jet is used to combine chemical and thermal processes for silicon ablation. We developed a numerical model to simulate heat transport and phase chang...

Laser Chemical Processing (LCP) is presented as a novel microstructuring method for multiple applications. Via the combination of a chemical liquid jet and a laser beam, thermochemical and photochemical reactions can be initiated. Due to the free choice of the chemistry for the carrier liquid and the laser source, efficient processes can be devised...

A numerical software has been developed to simulate heating, enthalpy-based phase changes and ablation of silicon during pulsed or continuous-wave laser irradiation. The unsteady heat transfer equation is solved by finite differences in two or three dimensions with full resolution of the thin liquid layer. An intelligent adaptive grid refinement an...

The introduction of selective emitters underneath the front contacts of solar cells can considerably increase the cell efficiency. Thus, cost-effective fabrication methods for this process step would help to reduce the cost per W p of silicon solar cells. Laser Chemical Processing (LCP) is based on the waterjet-guided laser (LaserMicroJet®) develop...

New passivation layers for the back side of silicon solar cells have to show high performance in terms of electrical passivation as well as high internal reflectivity. This optical performance is often shown as values for the back side reflectance Rb which describes the rear internal reflection. In this paper, we investigate in detail the meaning o...

In this paper, we review the device physics to explain the necessity of edge isolation as well as the various common methods for performing this important step. In order to assess these processes, different aspects have to be taken into consideration and will be discussed. Finally, experimental results of edge isolation on commercial multicrystalli...

In this paper we investigate different process types for multi-wire sawing of solar silicon wafers. These are the standard monodirectional wire movement as well as the reciprocating wire movement with SiC/PEG (polyethylene glycole) slurry. The third process is the diamond coated wire cutting with water-based slurry. We give a first answer to the qu...

In this paper we present different possibilities like QSSPC lifetime measurements, X-ray diffraction and defect etch to measure laser induced damage in silicon wafers. The lifetime measurement results of the laser chemical etching (LCE), Laser Micro Jettrade (LMJ) and a standard laser are plotted in a diagram. Furthermore the defect etch investigat...

This paper presents the application of the analytical model for locally contacted rear sides recently published by Fischer to the determination of recombination losses of solar cells with fixed metallization fraction, but varying contact pitch. After the successful experimental validation of the model on oxide-passivated solar cells with ohmic cont...

The laser-fired contact (LFC) process recently developed by Fraunhofer ISE is an elegant and cost-effective way to fabricate a dielectrically passivated rear surface for high-efficiency silicon solar cells. The performance of LFC cells is superior compared to standard PERC cells since aluminium is alloyed into the base under the contacts creating l...

In this paper, we present highly efficient laser-fired solar cells on very thin wafers (down to 34 \μm). These solar cells were processed in the Fraunhofer ISE cleanroom on mechanically thinned wafers. Since there exists the predominant opinion that thin wafer processing suffers from highly increased breakage, mechanical tests as well as breakage s...

Die Arbeit befasst sich mit hocheffizienten Solarzellenstrukturen für industrielles monokristallines Silicium-Material mit Diffusionslängen kleiner als 300 µm. Es werden zwei Wege vorgeschlagen: Die Verwendung ultradünner Wafer (bis zu 36 µm dünn) sowie die Realisierung einer Emitter-Wrap-Through-Struktur. Im Bereich der ultradünnen Solarzellen wer...

One of the most promising cell concepts for high efficiencies on medium quality base material is the emitter-wrap-through (EWT) solar cell. We fabricated solar cells on 1.25 /spl Omega/ cm FZ and 1.4 /spl Omega/ cm Cz(B) material. The performance of EWT, rear contacted cells (RCC) and random-pyramids passivated emitter and rear cells (RP-PERC) on C...

Recent experimental results of inverted pyramids passivated emitter and rear cells (IP-PERC) of varying thickness down to 63 /spl mu/m on FZ and Cz material are presented. The rear side contacts are made conventionally as well as by the laser-fired contacts (LFC) method. The V/sub oc/ dependence on cell thickness of annealed and degraded Cz is meas...

At Fraunhofer ISE the fabrication of high-efficiency solar cells was extended from a laboratory scale to a small pilot-line production. Primarily, the fabricated cells are used in small high-efficiency modules integrated in prototypes of solar-powered portable electronic devices such as cellular phones, handheld computers etc. Compared to other app...

Presents an outline of the work done in the EC co-funded project ACE Designs. The objective of this project was to develop rear contact solar cell designs and to demonstrate their applicability as an alternative crystalline silicon technology for industrial module production. An overview of the results is given with links to the most relevant, publ...

The goal of the project Alba is the development and fabrication of EWT solar cells on multi-crystalline silicon with a clearly increased cell efficiency compared to standard industrial Si cells. The project lays special focus on the development of industrially applicable processes. Exemplary realisation of advanced process steps for the fabrication...

DE 102009004902 B3 UPAB: 20100524 NOVELTY - Silicon-containing solids microstructuring and passivation involves guiding a fluid jet over area of solid, where the fluid jet contains precursor for passivation of the solid surface. A laser jet is coupled in the fluid jet, where the solid surface is heated locally by the laser jet and is partially stru...